docs: def _get_distance_term(self, C, rrup, mag):
          """
          Returns the distance scaling given in Equation (4), page 1569,
          with distance adjusted by the magnitude-dependent depth scaling
          factor given in Equation (6)
          """
          r_adj = np.sqrt(rrup ** 2.0 + (mag ** 2.0 - 3.1 * mag - 14.55) ** 2.)
          return C["c1"] * np.log10(r_adj) + C["c2"] * r_adj